Nicotine gum has been recently approved as a prescription drug to help smokers stop smoking. Despite both theoretical and clinical evidence that a substantial proportion of patients will persist in chronic use of the gum, a study of the self-administration properties of the gum has not been performed. In the first study of this proposal, the patterns of self-administration of nicotine gum will be determined among smokers seen in a general medical practice who follow FDA-approved guidelines for gum use. This study will use a double-blind placebo-controlled design to determine the incidence of chronic use of gum after the prescribed period and the relationship between chronic use and behavioral factors (e.g., history of abuse of other drugs. A second set of studies will test whether factors that control the self-administration of other drugs of abuse also control self-administration of nicotine gum. The factors to be studied are (1) dose (1 vs. 2 vs. 4 mg gum), (2) response cost (free vs. half price vs. full price gum), (3) schedule of self-administration (i.e., ad-lib vs. fixed times), and (4) duration of exposure (1 vs. 2 vs. 3 mo.). The studies proposed will provide the first experimental determination of how nicotine gum is actually used, the incidence of chronic use of the gum, and factors that can be used to identify smokers at increased risk of chronic use (Study 1), as well as prescription practices that can be used to reduce chronic use of nicotine gum (Studies 2-5).